The other night I finally finished my work for the day and pushed away from the computer. Feeling the tightness in my chest and noticing how my shoulders were rolled forward, I laid down on the hardwood floor and focused on breathing, stretching, and massaging muscles until my shoulder blades once more laid flat on my back. The obvious source of the discomfort was in my chest and shoulders, but as I followed lines of tension I found myself working on muscles in my forearm, which, as they relaxed, helped my shoulders to relax and open. What is the process here? How does a forearm muscles help tighten or relax the shoulder? It might seem strange since the muscles I was working on, the Flexor Digitorum, do not directly attach to the shoulder, or even the upper arm.

Flexor Digitorum: Notice how the muscle is shown attaching from the fingers to the ulna and radius. The fascial structures are not shown. Taken from "Anatomy of Movement" by Blandine Calais-Germain.

(Note: The book this is from, Anatomy of Movement, is a great introduction to what muscles are involved in specific motions. I learned a LOT from this book!)

A common over-simplification of the classical biomechanical model is that muscles attach directly to bones and that, as a result, one can calculate the force that a muscle is contracting with and assume that this force is applied to the bone which causes the bone to rotate around the fulcrum point of the joint that the muscle crosses.

Classic mechanical analysis of biomechanics

Classic Biomechanical Analysis

The problem with this view is that muscle does not attach directly to the bone, rather it directly interacts with the fascia – often called the connective tissue, which includes tendons and ligaments. Yet, as the traditional name “connective tissue” implies, the fascia is often oversimplified and treated as a simple connector between the muscle and the bone, much like a cable that directly transmits the force of the muscle to the bone. Here is a fairly traditional anatomical drawing of the knee that depicts this over simplified role of tendons and ligaments.

Classic anatomical drawing. Notice how the tendons directly connect a muscle to a bone.

Compare that with this next anatomical drawing, which shows more details of how the fibers of the fascia interact.

In this drawing, it is harder to say what the final effect of a muscle contraction will be. The muscle will pull on the fascia, but the fibers of the fascia interact with each other in a complex mesh and seem to attach to many locations. This is complicated by our bodies process of laying down collagen tissue which will “glue” neighboring muscles and ligaments together if they are not moved frequently enough (see My post on Fascia, Collagen, Motion, and Bodywork). To see the complexity, look at the fibers labeled “iliotibial band.” If you pulled on the top of this, what would happen? It splits into multiple branches attaching to various other structures that are also themselves affected by various other muscles. Pay attention to how most of the fascia in the knee connect to the patella (the knee cap). The patella is not anchored in place, rather it is “floating” in a web of tension from all the fascia connections, thus all muscles that connect to the patella directly impact the tension and flow of forces from all the other muscles and fascia which connect to the patella — i.e. it all connects!

Now, let us take this one level further and look at the following picture of the knee of a human cadaver. The Body Worlds Exhibit where I first saw this is an AMAZING experience and opened my mind to a lot of understanding by being able to see the full structure of the body in 3D.

Knee of a Cadaver, from Body Worlds Exhibit

What you see here are broad sheets of connective tissue to which the muscles attach. Looked at this way, it becomes clear that the exact impact of a muscle contraction will be distributed over a larger complex system of interacting forces.

With this in mind, let us look more closely at what fascia is. Fascia is the fibrous material that gives the ultimate structure of our bodies. Every muscle is surrounded by fascia, and the outer layer of the bones, called the periosteum, is also fascia. In fact, the fibers that surround the muscle are continuous through the tendon to the periosteum, as illustrated below.

The fibers of the fascia are continuous from around the muscle through the outer layer of bone

Putting aside the image of tendons and ligaments as simple “connective tissue” between the muscles and bones, a better visualization is a continuous web of fascia, within which the muscles and bones are suspended. This is made obvious by looking at how we develop. During the early stages of embryonic development the body is a network of fascia with approximately 660 pockets within which the muscles and bones will grow.

Returning to the question of how tightness in the forearm can affect the shoulder, we can now follow the flow of forces generated by a muscle. When a muscle contracts or is locked in a shortened position, it pulls towards the middle. The muscle’s pull doesn’t fully ground out into the bone to which it “attaches,” rather the force is transmitted into the fascial structures that it is part of. The force is then distributed further, some of it going into the bone, and much of it pulling on muscles on the other side of the joint which are part of the same fascial structure. Thus, a tight muscle in one part of your body can pull a joint further away out of alignment by transmitting force through the bodies fascial structures.

This perspective of the human body as a continuous web of tension is also sometimes called BioTensegrity. Tensegrities are a special form of structure which hold their shape via a continuous web of pre-stressed tension. There are many physical qualities to tensegrity structures which make them interesting from the perspective of understanding how we move so gracefully in through the world. A number of other posts on this blog go into depth on the tensegrity structures, how they apply to our bodies, and how they are relevant to robotics. Please see the Tensegrity category, or these specific posts:

Thank you for the amazing talk you gave at Cisco Switzerland today. I wasn’t familiar with the topic, but it really got me and I’m looking forwards to learning more about it. Will follow your blog closely!!

Great post! The fascia is actually a single tissue that covers the body from head to toe and connects its every part inextricably with one another. It acts like an individual wrapping for every internal part, keeping it separate from the rest. Largely ignored till recent times, mainly because of its undefined function and messy appearance, modern research has revealed the extent of the impact of fascia on muscle strength, bio mechanics and athletic performance. For more on how to maintain the fine balance between elasticity and tension in the muscle fascia to enable the best physical equilibrium please visit http://lovefitnesseducation.com/2012/08/21/understanding-muscle-fascia/

All my connective tissue is being agonisingly destroyed and I think the fascitis and fasciosis is the hardest to bear. In my case, as in many, it was caused by a few tablets of a (fluoro)quinolone antibiotic.

You can read about it on my blog, if interested. http://destruida-los-restos.blogspot.com.es/
It’s a deeply grieving to be a healthy person, whose body worked so beautifully, and to be rotting slowly just to give profits to the pharmatrade.

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About BeingHuman

Greetings!
Here you will find my thoughts on being human, based on my ongoing research into robotic and human motion, neuroscience, physiology, and machine learning. You will also find videos of my talks and papers from the Dynamic Tensegrity Robotics Lab which I lead at the NASA Ames Research Center.

Archive of all past posts

Archive of all past posts

My Favorite Ergonomic Equipment

Based on my understanding of human physiology and motion, here are some quick reviews on my favorite ergonomic tools. These are the ones I use at home and at work. I will add more in-depth posts discussing the alignment theory as I get them written.

FitBall Sitting Disc
Sitting Discs are a great way to train for Active Sitting. By destabilizing the surface you are sitting on, they engage your core muscles and keep you in dynamic motion while your body actively balances on the disk. I recommend the larger 15" disc. In Depth Review

Salli Saddle Stool
The Salli saddle stools are one of the best stools for Active Sitting. They hold your pelvis upright, so that your spine can be well aligned with gravity, while also allowing your knees to be lower than your hips to keep your hamstrings and hip-flexors from shortening. Actively sitting takes effort, so increase your time in the saddle slowly.

3M Ergonomic Mouse
The vertical design keeps the arm in a well aligned neutral "handshake" position that prevents the shoulder from rolling forward. By keeping your shoulders back and the scapula flat on your back you avoid many of the common sources of wrist pain. This is the biggest bang for your buck if you are having wrist pain. It comes in small and large sizes (small is linked below). Sadly, I have only seen it for right hands.

ErgoMagic Keyboard
Like the 3M mouse above, this keyboard allows you to have your hands in a more neutral vertical position which reduces many of the problems associated with wrist and shoulder pain. It also allows you to spread the key pads to be at shoulder width so that you don't have to twist your wrist like on a straight keyboard.

Sit-Stand Desk
A sit stand desks allows you to dance while working! It also allows you change between a variety of different sitting options and standing so that you don't get stuck in one position. The best option that I have found is from GeekDesk.com. I have two from them and they are the cheapest and have held up well. You can save even more money by buying just the base frame from GeekDesk and getting the table top from Ikea. You save on price and shipping is significantly less this way.

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Books I Recommend

Sync: How Order Emerges From Chaos In the Universe, Nature, and Daily Life
This book blew my mind.
Really -- this was probably one of the most influential books I've read in a decade. This points straight at the heart of what we intuitively recognize as the difference between living breathing organic aspects of nature and the mechanistic nature of human engineered system. It all boils down to oscillators and their ability to synchronize. This basic mathematical property is the basis for all the order that we see in the world -- and our ability to move -- and our ability to relate to each other -- and really everything. This is an easy and engaging read, and you will come away with new eyes for the world.

Anatomy of Movement
This was the best book I have read for learning about the function of my own body and is endlessly useful for anyone who is alive and moving in the world. Ever have pain when you make a specific motion and wonder what is going on? This book will help you isolate the muscles responsible for that motion. By showing how each muscle moves your body under different conditions, you will learn their *use* rather than just memorizing a bunch of names.

Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists
This book is great to see and understand the complex network of tension in the living body, and to learn about fascia and how it works.

Rhythms of the Brain
This recently published book covers cutting edge theories of how the brain works. The key focus is on how the brain relies heavily on coupled oscillatory networks, timing loops, and synchronization. It also discusses how the activity in the brain can be viewed as a dynamic tensegrity structure. A more technical book, but well worth the effort!